Lithium recovery equipment and process for concentrating and purifying salt-making mother liquor

Abstract

The invention discloses equipment and a process for concentrating, purifying and recycling lithium from salt-making mother liquor, and relates to the technical field of membrane purification and separation.The equipment for concentrating, purifying and recycling lithium comprises an adsorption unit, a membrane unit, an MVR evaporation unit, a crystallization separation unit and a condenser, the adsorption unit is used for adsorbing lithium ions from the salt-making mother liquor, and the membrane unit is connected to the downstream of the adsorption unit; the membrane unit is used for separating impurities and pre-concentrating a lithium chloride solution, and the MVR evaporation unit is connected to the downstream of the membrane unit, comprises a mechanical vapor recompression evaporator and a preheating device, and is used for concentrating the lithium chloride solution to 18-30 g / L; the crystallization separation unit is connected to the downstream of the MVR evaporation unit and used for separating out and separating high-purity lithium chloride crystals, and the condenser is used for collecting and recycling water vapor generated by the crystallization separation unit.

Description

Technical Field

[0001] The present invention relates to the technical field of membrane purification and separation, and in particular to a device and process for recovering lithium from concentrated and purified salt-making mother liquor. Background Art

[0002] In the field of lithium resource recovery, traditional processes mainly rely on adsorption, membrane separation, evaporation concentration and crystallization technologies, but the following key issues still exist:

[0003] 1. Inefficient adsorption process: Traditional fixed-bed ion exchange processes use a single resin bed in a staged process (adsorption, regeneration, and washing are performed sequentially). This results in low resin utilization (approximately 30% to 50%), a lengthy regeneration process, and high chemical consumption. Furthermore, solution residue is prone to occur during fixed-bed switching, affecting lithium ion adsorption efficiency.

[0004] 2. Limitations of membrane separation technology: Single membrane treatment (such as using only reverse osmosis membrane) is difficult to cope with complex mother liquor systems. Tiny particles, organic matter and divalent calcium and magnesium ions can easily cause membrane contamination or penetration, resulting in an increase in the load of subsequent evaporation units and insufficient purity of the concentrate (large fluctuations in lithium ion concentration).

[0005] 3. High-energy consumption evaporation process: Conventional multi-effect evaporation technology relies on external steam heating, with low energy utilization (high steam consumption), and high-temperature operation can easily cause decomposition or scaling of lithium chloride solution, affecting the purity of the final product.

[0006] 4. Poor crystallization process stability: In traditional vacuum crystallization tanks, the solution flashes and becomes locally oversaturated, causing crystals to adhere to the tank walls and form scars. This requires frequent downtime for manual cleaning, leading to production interruptions and increased equipment maintenance costs. Furthermore, uneven crystal size distribution affects subsequent separation efficiency.

[0007] The crystallization unit tried to use a mechanical scraping device, but the structure was complex and it was difficult to dynamically respond to changes in the amount of crystal attachment, so it still relied on manual intervention.

[0008] In summary, the existing technology urgently needs a lithium recovery process and equipment that is efficient, energy-saving, continuous, stable, and resource-recycling, so as to break through bottlenecks such as adsorption efficiency, energy consumption limitations, crystallization continuity, and environmental protection. Summary of the Invention

[0009] The purpose of the present invention is to provide a lithium recovery device and process for concentrating and purifying salt production mother liquor to solve the problems raised in the prior art.

[0010] To achieve the above-mentioned objectives, the present invention provides the following technical solutions: a concentrated and purified lithium recovery device includes an adsorption unit, a membrane unit, an MVR evaporation unit, a crystallization separation unit and a condenser. The adsorption unit is used to adsorb lithium ions from the salt production mother liquor. The membrane unit is connected downstream of the adsorption unit. The membrane unit is used to separate impurities and pre-concentrate the lithium chloride solution. The MVR evaporation unit is connected downstream of the membrane unit and includes a mechanical vapor recompression evaporator and a preheating device for concentrating the lithium chloride solution to 18-30 g / L. The crystallization separation unit is connected downstream of the MVR evaporation unit for precipitating and separating high-purity lithium chloride crystals. The condenser is used to collect and reuse the water vapor generated by the crystallization separation unit.

[0011] Furthermore, the adsorption unit adopts a continuous desorption process.

[0012] The principle of the continuous desorption process is to divide the entire section of resin in the original fixed bed into several sections. Different sections of resin play different roles at the same time, so that the exchange, water washing, regeneration and other sections of the original fixed bed are integrated into a set of system equipment, making use of some of the originally idle resin, greatly improving the resin utilization rate, and reducing the consumption of chemicals through an effective connection operation mode.

[0013] Furthermore, the membrane unit is sequentially provided with a microfiltration membrane, an ultrafiltration membrane, a nanofiltration membrane and a reverse osmosis membrane. The nanofiltration membrane intercepts divalent calcium and magnesium ions, and the reverse osmosis membrane concentrates the lithium chloride solution to 5-6 g / L, and the produced water is recycled to the adsorption unit and the membrane unit.

[0014] The decomposed lithium chloride solution contains calcium, magnesium, calcium sulfate, and tiny particles. After microfiltration, ultrafiltration, and nanofiltration, the tiny particles and divalent ions are separated and stored in a buffer tank before being reinjected into the mine. The lithium-containing solution then enters a reverse osmosis membrane, raising the lithium concentration from 0.5-0.6 g / L to 5-6 g / L. It then enters a sodium ion exchange resin to further remove calcium and magnesium from the lithium chloride solution. The reverse osmosis pure water system, which removes the lithium adsorption resin, and the microfiltration, ultrafiltration, and nanofiltration systems serve as the water source.

[0015] Furthermore, in the MVR evaporation unit, the secondary steam is compressed by the compressor and circulated as a heat source, the evaporation temperature is controlled at 95-120°C, and the concentration of the lithium chloride concentrate is 18-30g / L.

[0016] The MVR unit uses an MVR evaporator to concentrate lithium chloride. MVR is an energy-saving technology that recycles the energy of its own secondary steam, thereby reducing the need for external energy. The secondary steam from the evaporator is compressed by a compressor, increasing its pressure, temperature, and enthalpy. It is then scrubbed in a scrubber and sent to the evaporator's heating chamber for use as heating steam, maintaining the boiling state of the feed liquid. The heating steam itself condenses into water, fully utilizing the steam's latent heat. Except for startup, steam generation is essentially unnecessary throughout the evaporation process; it is only used to compensate for heat losses, which account for approximately 5% of the total steam volume.

[0017] Furthermore, the crystallization separation unit includes a circulation pump, a crystallization tank, an attachment component and a recoil component. The circulation pump is connected to the crystallization tank through a pipeline. The circulation pump is used to push the lithium chloride liquid in the circulating crystallization tank. The crystallization tank is provided with a discharge port and a steam outlet. The attachment component and the recoil component are located in the crystallization tank. The attachment component is used to determine the number of grains attached to the wall during the crystallization process. The recoil component automatically peels off the attached grains by adjusting the concentration of the liquid.

[0018] The crystallizer uses a vacuum system to create a negative pressure, which flashes the liquid inside the tank, evaporating water and cooling the temperature. The solubility of lithium chloride decreases with decreasing temperature. As water evaporation decreases, the temperature drops again, and lithium chloride crystals precipitate. The lithium chloride liquid in the tank is circulated by a circulating pump; however, the rapid evaporation of the solvent near the tank wall leads to localized supersaturation, causing crystals to nucleate and grow on the wall, affecting evaporation efficiency and requiring frequent downtime for cleaning, reducing production efficiency. By placing a movable attachment component on the inner wall of the crystallizer, crystals grow onto the attachment component. The system then detects the number of crystals on the attachment component and automatically controls the recoil component to remove the attached crystals, thereby ensuring production efficiency.

[0019] Furthermore, a chute is provided in the crystallization tank, and the attachment component includes an arc-shaped wall, a slider, an adjustment spring and a displacement sensor. The arc-shaped wall is tightly connected to the slider. Several arc-shaped walls are arranged along the inner wall of the crystallization tank. Several arc-shaped walls form a whole circle. Adjacent arc-shaped walls can move relative to each other. The slider is slidably connected to the chute, one end of the adjustment spring is tightly connected to the slider, and the other end of the adjustment spring is tightly connected to the inner wall of the chute. The displacement sensor is tightly connected to the slider. The longer the distance the slider moves downward, the more grains are attached to the arc-shaped wall.

[0020] When the crystals grow onto the curved wall, the overall weight of the curved wall increases. Under the action of gravity, the curved wall will deflect downward, thereby driving the slider to slide downward along the slide groove, causing the adjustment spring to be compressed. The more crystals attached to the curved wall, the greater the weight, and the longer the distance the slider moves downward. That is, the longer the distance the displacement sensor detects that the slider moves downward, the more crystals are attached to the curved wall.

[0021] Furthermore, the recoil components are provided in several groups in the crystallization tank, and the positions of the recoil components correspond to the attachment components;

[0022] Several backflush components include a liquid inlet ring, a liquid distribution plate and an adjusting block. The liquid inlet ring is tightly connected to the crystallization tank, and the inlet of the liquid inlet ring is connected to the water outlet of the condenser. The crystallization tank is also provided with a card slot and a connecting slot. The connecting slot is connected to the outlet of the liquid inlet ring. The liquid distribution plate is clamped with the card slot. The liquid distribution plate is provided with a liquid inlet groove, a liquid outlet and an arc groove. The liquid inlet groove is connected to the connecting groove, and the liquid outlet is connected to the liquid inlet groove. The adjusting block is slidably connected to the arc groove. The adjusting block is provided with a backflush port, which is connected to the liquid outlet and faces the arc wall.

[0023] When the number of crystals attached to the curved wall of an attachment assembly at a certain position is too large, the backflush assembly at the corresponding position is started, and the condensed water generated by the condenser is pumped into the liquid inlet ring by a water pump, and then flows into the connecting groove, thereby entering the liquid inlet groove in the distribution plate, and finally flows to the backflush port through the liquid outlet, thereby generating an upward backflush water flow, which impacts the surface of the curved wall and removes the attached crystals through the impact force of the water flow; and the backflush assembly introduces condensed water to reduce the concentration of the lithium chloride slurry near the curved wall, so that the crystals dissolve, that is, by combining backflush and reducing the concentration of the solution at the curved wall, the crystals attached to the wall are automatically peeled off, thereby preventing crystal adhesion and improving production efficiency.

[0024] Furthermore, the recoil assembly also includes an electromagnet and a support spring, the electromagnet is fastened to the inner wall of the arc groove, one end of the support spring is fastened to the adjustment block, and the other end of the support spring is fastened to the inner wall of the arc groove, and the adjustment block is made of ferromagnetic material.

[0025] The backflush port and the liquid outlet are arranged alternately.

[0026] The generation of crystals is uneven, and the number of crystals attached to the arc-shaped wall at different positions will be uneven. Through the staggered arrangement of back-blowing ports and liquid outlets, the current transmitted to the electromagnet is increased for positions with a large number of attached crystals. The electromagnet cooperates with the ferromagnetic adjustment block to make the adjustment block deflect toward the electromagnet along the arc groove. The overlapping area of ​​the back-blowing port and the liquid outlet will increase, and the outflowing water flow rate will increase, thereby increasing the recoil force at positions with more crystals attached, and making the concentration of lithium chloride slurry on the wall at the corresponding position drop faster, thereby promoting the peeling of the crystals.

[0027] Furthermore, the recovery process comprises the following steps:

[0028] (1) Adsorption step: The mother liquor of salt production is passed through a continuous ion exchange system, and lithium ions are selectively adsorbed by an improved weak acid resin (the improved weak acid resin adopts a chelating resin that adsorbs lithium ions), and a low-concentration lithium chloride solution is obtained after decomposition;

[0029] (2) Membrane concentration step: The lysate is sequentially filtered through microfiltration and ultrafiltration to remove particulate matter, then separated by nanofiltration to separate calcium and magnesium ions, and finally concentrated to 5-6 g / L through a reverse osmosis membrane;

[0030] (3) MVR evaporation step: The concentrated liquid is preheated and enters the MVR evaporator, where it is further concentrated to 18-30 g / L using the latent heat of secondary steam;

[0031] (4) Crystallization and separation step: The concentrated liquid is cooled and crystallized in a vacuum flash crystallization tank. The crystal slurry is settled, washed, and dehydrated to obtain lithium chloride product. The overflow liquid is returned to the previous step for recycling treatment.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1. Highly efficient and energy-saving MVR evaporation technology: Through secondary steam recycling, reliance on external heat sources is reduced, steam utilization is increased by approximately 95%, and energy consumption is significantly reduced. Continuous desorption process: The resin operates synchronously in stages (adsorption, regeneration, and water washing), reducing chemical consumption and resin idle time, thereby improving overall efficiency.

[0034] 2. Resource recycling and closed-loop water circulation: Reverse osmosis pure water is reused in the adsorption and membrane systems, and condensate is used to backwash components, reducing fresh water consumption and achieving efficient water resource utilization. Impurity resource utilization: Impurity solutions such as calcium and magnesium separated by the membrane unit are reinjected into the mine, avoiding wastewater discharge and reducing the environmental burden.

[0035] 3. Intelligent crystallization control: The crystallization separation unit's adhesion component (displacement sensor monitoring) is combined with a recoil component (condensate water recoil + concentration adjustment) to prevent crystals from adhering to the tank wall, ensuring continuous precipitation of high-purity lithium chloride crystals and improving recovery rates. The automatic recoil system dynamically adjusts the recoil water flow intensity (precisely controlled by an electromagnet + adjustment block) based on the amount of crystal adhesion, eliminating the need for downtime for cleaning and ensuring production continuity. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic diagram of the process flow of the present invention;

[0037] Figure 2 Schematic diagram of the crystallization separation unit of the present invention;

[0038] Figure 3 It is a partial cross-sectional view of the crystallization tank;

[0039] Figure 4 for Figure 3 A local enlarged view of point A;

[0040] Figure 5 for Figure 3 A partial enlarged view of point B;

[0041] Figure 6 is a schematic diagram of the recoil assembly;

[0042] Figure 7 for Figure 6 A partial enlarged view of point C;

[0043] Figure 8 Schematic diagram of the flow direction of the backflush component.

[0044] In the figure: 1. Adsorption unit; 2. Membrane unit; 3. MVR evaporation unit; 4. Crystallization separation unit; 5. Condenser; 41. Circulation pump; 42. Crystallization tank; 421. Discharge port; 422. Steam outlet; 423. Slide; 424. Card slot; 425. Connecting slot; 43. Attachment assembly; 431. Arc wall; 432. Slider; 433. Adjustment spring; 434. Displacement sensor; 44. Backflush assembly; 441. Liquid inlet ring; 442. Liquid distribution plate; 4421. Liquid inlet slot; 4422. Liquid outlet; 4423. Arc slot; 443. Adjustment block; 4431. Backflush port; 444. Electromagnet; 445. Support spring. DETAILED DESCRIPTION

[0045] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0046] Example: Figures 1-8 As shown, the present invention provides a lithium recovery device and process technology solution for concentrating and purifying salt production mother liquor. The lithium recovery device for concentrating and purifying lithium includes an adsorption unit 1, a membrane unit 2, an MVR evaporation unit 3, a crystallization separation unit 4 and a condenser 5. The adsorption unit 1 is used to adsorb lithium ions from the salt production mother liquor. The membrane unit 2 is connected to the downstream of the adsorption unit 1. The membrane unit 2 is used to separate impurities and pre-concentrate the lithium chloride solution. The MVR evaporation unit 3 is connected to the downstream of the membrane unit 2, including a mechanical vapor recompression evaporator and a preheating device, which is used to concentrate the lithium chloride solution to 18-30 g / L; the crystallization separation unit 4 is connected to the downstream of the MVR evaporation unit 3, which is used to precipitate and separate high-purity lithium chloride crystals. The condenser 5 is used to collect and reuse the water vapor generated by the crystallization separation unit 4.

[0047] Adsorption unit 1 adopts a continuous desorption process.

[0048] The principle of the continuous desorption process is to divide the entire section of resin in the original fixed bed into several sections. Different sections of resin play different roles at the same time, so that the exchange, water washing, regeneration and other sections of the original fixed bed are integrated into a set of system equipment, making use of some of the originally idle resin, greatly improving the resin utilization rate, and reducing the consumption of chemicals through an effective connection operation mode.

[0049] Membrane unit 2 is sequentially provided with a microfiltration membrane, an ultrafiltration membrane, a nanofiltration membrane and a reverse osmosis membrane. The nanofiltration membrane intercepts divalent calcium and magnesium ions, and the reverse osmosis membrane concentrates the lithium chloride solution to 5-6 g / L, and the produced water is recycled to the adsorption unit 1 and the membrane unit 2.

[0050] The decomposed lithium chloride solution contains calcium, magnesium, calcium sulfate, and tiny particles. After microfiltration, ultrafiltration, and nanofiltration, the tiny particles and divalent ions are separated and stored in a buffer tank before being reinjected into the mine. The lithium-containing solution then enters a reverse osmosis membrane, raising the lithium concentration from 0.5-0.6 g / L to 5-6 g / L. It then enters a sodium ion exchange resin to further remove calcium and magnesium from the lithium chloride solution. The reverse osmosis pure water system, which removes the lithium adsorption resin, and the microfiltration, ultrafiltration, and nanofiltration systems serve as the water source.

[0051] In the MVR evaporation unit 3, the secondary steam is compressed by the compressor and then circulated as a heat source. The evaporation temperature is controlled at 95-120°C, and the concentration of the lithium chloride concentrate is 18-30g / L.

[0052] The MVR unit uses an MVR evaporator to concentrate lithium chloride. MVR is an energy-saving technology that recycles the energy of its own secondary steam, thereby reducing the need for external energy. The secondary steam from the evaporator is compressed by a compressor, increasing its pressure, temperature, and enthalpy. It is then scrubbed in a scrubber and sent to the evaporator's heating chamber for use as heating steam, maintaining the boiling state of the feed liquid. The heating steam itself condenses into water, fully utilizing the steam's latent heat. Except for startup, steam generation is essentially unnecessary throughout the evaporation process; it is only used to compensate for heat losses, which account for approximately 5% of the total steam volume.

[0053] The crystallization separation unit 4 includes a circulation pump 41, a crystallization tank 42, an attachment component 43 and a recoil component 44. The circulation pump 41 is connected to the crystallization tank 42 through a pipeline. The circulation pump 41 is used to push the lithium chloride liquid in the circulating crystallization tank 42. The crystallization tank 42 is provided with a discharge port 421 and a steam outlet 422. The attachment component 43 and the recoil component 44 are located in the crystallization tank 42. The attachment component 43 is used to determine the number of grains attached to the wall during the crystallization process. The recoil component 44 automatically peels off the attached grains by adjusting the concentration of the liquid.

[0054] Crystallizer 42 is vacuumed by a vacuum system, generating negative pressure, which causes the liquid in the tank to flash, evaporate water, and cool down. The solubility of lithium chloride decreases with decreasing temperature. As water evaporation decreases, the temperature drops again, and lithium chloride crystals precipitate. The lithium chloride liquid in the tank is circulated by a circulating pump 41; however, the solution near the tank wall rapidly evaporates, leading to increased local supersaturation, which promotes crystal nucleation and growth on the wall, affecting the evaporation effect and requiring frequent shutdowns for cleaning, reducing production efficiency. By arranging a movable attachment assembly 43 on the inner wall of crystallizer 42, crystals grow onto attachment assembly 43. Then, by detecting the number of crystals on attachment assembly 43, a recoil assembly 44 is automatically controlled to remove the attached crystals, thereby ensuring production efficiency.

[0055] A chute 423 is provided in the crystallization tank 42, and the attachment component 43 includes a curved wall 431, a slider 432, an adjusting spring 433 and a displacement sensor 434. The curved wall 431 is tightly connected to the slider 432. Several curved walls 431 are arranged along the inner wall of the crystallization tank 42. Several curved walls 431 form a whole circle. Adjacent curved walls 431 can move relative to each other. The slider 432 is slidingly connected to the chute 423. One end of the adjusting spring 433 is tightly connected to the slider 432, and the other end of the adjusting spring 433 is tightly connected to the inner wall of the chute 423. The displacement sensor 434 is tightly connected to the slider 432. The longer the distance that the slider 432 moves downward, the more grains are attached to the curved wall 431.

[0056] When the crystals grow onto the curved wall 431 , the overall weight of the curved wall 431 increases. Under the action of gravity, the curved wall 431 will deflect downward, thereby driving the slider 432 to slide downward along the slide groove 423 , causing the adjustment spring 433 to be compressed. The more crystals attached to the curved wall 431 , the greater their weight, and the longer the distance the slider 432 moves downward. That is, the longer the distance the displacement sensor 434 detects that the slider 432 moves downward, the more crystals are attached to the curved wall 431 .

[0057] The recoil components 44 are provided in a plurality of groups in the crystallization tank 42, and the positions of the recoil components 44 correspond to the attachment components 43;

[0058] Several backflush components 44 include a liquid inlet ring 441, a liquid distribution plate 442 and an adjusting block 443. The liquid inlet ring 441 is tightly connected to the crystallizer 42. The inlet of the liquid inlet ring 441 is connected to the water outlet of the condenser 5. The crystallizer 42 is also provided with a card slot 424 and a connecting slot 425. The connecting slot 425 is connected to the outlet of the liquid inlet ring 441. The liquid distribution plate 442 is engaged with the card slot 424. The liquid distribution plate 442 is provided with a liquid inlet groove 4421, a liquid outlet 4422 and an arc groove 4423. The liquid inlet groove 4421 is connected to the connecting slot 425. The liquid outlet 4422 is connected to the liquid inlet groove 4421. The adjusting block 443 is slidably connected to the arc groove 4423. The adjusting block 443 is provided with a backflush port 4431. The backflush port 4431 is connected to the liquid outlet 4422, and the backflush port 4431 faces the arc wall 431.

[0059] When the number of crystals attached to the curved wall 431 of the attachment component 43 at a certain position is too large, the backflush component 44 at the corresponding position is started, and the condensed water generated by the condenser 5 is pumped into the liquid inlet ring 441 by the water pump, and then flows into the connecting groove 425, thereby entering the liquid inlet groove 4421 in the liquid distribution plate 442, and finally flows to the backflush port 4431 through the liquid outlet 4422, thereby generating an upward backflush water flow, which impacts the surface of the curved wall 431 and removes the attached crystals by the impact force of the water flow; and the backflush component 44 reduces the concentration of the lithium chloride slurry near the curved wall 431 by introducing condensed water, so that the crystals are dissolved, that is, by combining backflush and reducing the concentration of the solution at the curved wall 431, the crystals attached to the wall surface are automatically peeled off, thereby preventing crystal adhesion and improving production efficiency.

[0060] The recoil assembly 44 also includes an electromagnet 444 and a support spring 445. The electromagnet 444 is fastened to the inner wall of the arc groove 4423. One end of the support spring 445 is fastened to the adjustment block 443. The other end of the support spring 445 is fastened to the inner wall of the arc groove 4423. The adjustment block 443 is made of ferromagnetic material.

[0061] The backflush port 4431 and the liquid outlet 4422 are arranged alternately.

[0062] The generation of crystals is uneven, and the number of crystals attached to the arc-shaped wall 431 at different positions will be uneven. Through the staggered arrangement of the back-blowing port 4431 and the liquid outlet 4422, the current transmitted to the electromagnet 444 is increased for the positions with a large number of attached crystals. The electromagnet 444 cooperates with the ferromagnetic adjustment block 443 to make the adjustment block 443 deflect along the arc-shaped groove 4423 toward the side of the electromagnet 444. The overlapping area of ​​the back-blowing port 4431 and the liquid outlet 4422 will increase, so that the outflowing water flow rate will increase, thereby increasing the recoil force at the position where more crystals are attached, and making the concentration of the lithium chloride slurry on the wall at the corresponding position drop faster, thereby promoting the peeling of the crystals.

[0063] The recycling process includes the following steps:

[0064] (1) Adsorption step: The mother liquor of salt production is passed through a continuous ion exchange system, and lithium ions are selectively adsorbed by an improved weak acid resin (the improved weak acid resin adopts a chelating resin that adsorbs lithium ions), and a low-concentration lithium chloride solution is obtained after decomposition;

[0065] (2) Membrane concentration step: The lysate is sequentially filtered through microfiltration and ultrafiltration to remove particulate matter, then separated by nanofiltration to separate calcium and magnesium ions, and finally concentrated to 5-6 g / L through a reverse osmosis membrane;

[0066] (3) MVR evaporation step: The concentrated liquid is preheated and enters the MVR evaporator, where it is further concentrated to 18-30 g / L using the latent heat of secondary steam;

[0067] (4) Crystallization and separation step: The concentrated liquid is cooled and crystallized in a vacuum flash crystallization tank. The crystal slurry is settled, washed, and dehydrated to obtain lithium chloride product. The overflow liquid is returned to the previous step for recycling treatment.

[0068] The working principle of the present invention: the adsorption unit 1 adopts a continuous desorption process to run the resin in sections (exchange, water washing, and regeneration are carried out simultaneously) to improve the resin utilization rate and reduce chemical consumption. Lithium ions are adsorbed from the salt production mother liquor to form a preliminary lithium-rich solution; the membrane unit 2 passes through the microfiltration membrane (to remove tiny particles), ultrafiltration membrane (to separate large molecular impurities), nanofiltration membrane (to intercept divalent calcium and magnesium ions) and reverse osmosis membrane (to concentrate the lithium chloride solution to 5-6g / L) in sequence, and the treated lithium-rich solution enters the subsequent unit, the impurity liquid is reinjected into the mine, and the pure water is reused for adsorption and membrane systems; the MVR evaporation unit 3 uses mechanical vapor recompression technology (MVR) to compress and heat the secondary steam and circulate it as a heat source to further concentrate the lithium chloride solution to 18-30g / L (preferably 25g / L), and the evaporation temperature is controlled at 95-120°C;

[0069] In crystallizer 42, flash evaporation lowers the temperature and solubility, prompting the precipitation of lithium chloride crystals. The attachment assembly (curved wall + displacement sensor) monitors the amount of crystals adhering to the wall in real time. When excessive crystals are present, the recoil assembly triggers a recoil flush using condensed water, combined with concentration dilution (reducing local solution concentration), to automatically remove the attached crystals, avoiding downtime for cleaning. The recoil water flow intensity is dynamically adjusted by an electromagnet in conjunction with a regulating block, precisely addressing uneven crystal distribution.

[0070] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be included therein. Any reference sign in a claim should not be construed as limiting the claim to which it relates.

Claims

1. A lithium recovery device for concentrating and purifying salt production mother liquor, characterized by: The concentrated and purified lithium recovery equipment comprises an adsorption unit (1), a membrane unit (2), an MVR evaporation unit (3), a crystallization separation unit (4) and a condenser (5). The adsorption unit (1) is used to adsorb lithium ions from salt production mother liquor. The membrane unit (2) is connected downstream of the adsorption unit (1). The membrane unit (2) is used to separate impurities and pre-concentrate lithium chloride solution. The MVR evaporation unit (3) is connected downstream of the membrane unit (2) and comprises a mechanical vapor recompression evaporator and a preheating device, and is used to concentrate the lithium chloride solution to 18-30 g / L. The crystallization separation unit (4) is connected downstream of the MVR evaporation unit (3) and is used to precipitate and separate high-purity lithium chloride crystals. The condenser (5) is used to collect and reuse the water vapor generated by the crystallization separation unit (4).

2. The lithium recovery equipment for concentrating and purifying salt production mother liquor according to claim 1, characterized in that: The adsorption unit (1) adopts a continuous desorption process.

3. The lithium recovery equipment for concentrating and purifying salt production mother liquor according to claim 1, characterized in that: The membrane unit (2) is provided with a microfiltration membrane, an ultrafiltration membrane, a nanofiltration membrane and a reverse osmosis membrane in sequence. The nanofiltration membrane intercepts divalent calcium and magnesium ions, and the reverse osmosis membrane concentrates the lithium chloride solution to 5-6 g / L, and the produced water is recycled to the adsorption unit (1) and the membrane unit (2).

4. The lithium recovery equipment for concentrating and purifying salt production mother liquor according to claim 1, characterized in that: In the MVR evaporation unit (3), the secondary steam is compressed by the compressor and then circulated as a heat source, the evaporation temperature is controlled at 95-120° C., and the concentration of the lithium chloride concentrate is 18-30 g / L.

5. The lithium recovery equipment for concentrating and purifying salt production mother liquor according to claim 1, characterized in that: The crystallization separation unit (4) comprises a circulation pump (41), a crystallization tank (42), an attachment assembly (43) and a backwash assembly (44); the circulation pump (41) is connected to the crystallization tank (42) through a pipeline; the circulation pump (41) is used to push the lithium chloride liquid in the circulating crystallization tank (42); the crystallization tank (42) is provided with a discharge port (421) and a steam outlet (422); the attachment assembly (43) and the backwash assembly (44) are located in the crystallization tank (42); the attachment assembly (43) is used to determine the number of crystal grains attached to the wall during the crystallization process; and the backwash assembly (44) automatically peels off the attached crystal grains by adjusting the concentration of the liquid.

6. The lithium recovery equipment for concentrating and purifying salt production mother liquor according to claim 5, characterized in that: A chute (423) is provided in the crystallization tank (42), and the attachment component (43) includes an arcuate wall (431), a slider (432), an adjustment spring (433) and a displacement sensor (434). The arcuate wall (431) is tightly connected to the slider (432), and a plurality of arcuate walls (431) are arranged along the inner wall of the crystallization tank (42). The plurality of arcuate walls (431) form a full circle, and adjacent arcuate walls (431) can move relative to each other. The slider (432) is slidably connected to the chute (423), one end of the adjustment spring (433) is tightly connected to the slider (432), and the other end of the adjustment spring (433) is tightly connected to the inner wall of the chute (423). The displacement sensor (434) is tightly connected to the slider (432), and the longer the distance that the slider (432) moves downward is detected by the displacement sensor (434), the more grains are attached to the arcuate wall (431).

7. The lithium recovery equipment for concentrating and purifying salt production mother liquor according to claim 6, characterized in that: The recoil components (44) are provided in a plurality of groups in the crystallization tank (42), and the positions of the plurality of recoil components (44) correspond to the attachment components (43); The recoil components (44) include a liquid inlet ring (441), a liquid distribution plate (442) and an adjusting block (443). The liquid inlet ring (441) is tightly connected to the crystallization tank (42). The inlet of the liquid inlet ring (441) is connected to the water outlet of the condenser (5). The crystallization tank (42) is also provided with a card slot (424) and a connecting groove (425). The connecting groove (425) is connected to the outlet of the liquid inlet ring (441). The liquid distribution plate (442) is connected to the card slot (424). The liquid distribution plate (442) is connected to the card slot (424). 42) is provided with a liquid inlet groove (4421), a liquid outlet (4422) and an arc-shaped groove (4423), the liquid inlet groove (4421) is communicated with the connecting groove (425), the liquid outlet (4422) is communicated with the liquid inlet groove (4421), the regulating block (443) is slidably connected to the arc-shaped groove (4423), and the regulating block (443) is provided with a backflush port (4431), the backflush port (4431) is communicated with the liquid outlet (4422), and the backflush port (4431) faces the arc-shaped wall (431).

8. The lithium recovery equipment for concentrating and purifying salt production mother liquor according to claim 7, characterized in that: The recoil assembly (44) further comprises an electromagnet (444) and a support spring (445), wherein the electromagnet (444) is fixedly connected to the inner wall of the arc-shaped slot (4423), one end of the support spring (445) is fixedly connected to the adjustment block (443), and the other end of the support spring (445) is fixedly connected to the inner wall of the arc-shaped slot (4423), and the adjustment block (443) is made of ferromagnetic material.

9. The lithium recovery equipment for concentrating and purifying salt production mother liquor according to claim 7, characterized in that: The backflush port (4431) and the liquid outlet (4422) are arranged alternately.

10. The recovery process of a lithium recovery device for concentrating and purifying salt production mother liquor according to claim 9, characterized in that: The recovery process comprises the following steps: (1) Adsorption step: The mother liquor of salt production is passed through a continuous ion exchange system, and lithium ions are selectively adsorbed by an improved weak acid resin, and a low concentration lithium chloride solution is obtained after desorption; (2) Membrane concentration step: The lysate is sequentially filtered through microfiltration and ultrafiltration to remove particulate matter, then separated by nanofiltration to separate calcium and magnesium ions, and finally concentrated to 5-6 g / L through a reverse osmosis membrane; (3) MVR evaporation step: The concentrated liquid is preheated and enters the MVR evaporator, where it is further concentrated to 18-30 g / L using the latent heat of secondary steam; (4) Crystallization and separation step: The concentrated liquid is cooled and crystallized in a vacuum flash crystallization tank. The crystal slurry is settled, washed, and dehydrated to obtain lithium chloride product. The overflow liquid is returned to the previous step for recycling treatment.

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